A computer program listing appendix containing an embodiment of a software program according to the present invention is included in this specification, the contents of which is incorporated herein for all purposes. The computer program listing appendix contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyrights whatsoever.
The present invention relates to geographic positioning systems and databases.
Geographic positioning technology, such as the Global Positioning System (GPS), involves the use of a constellation of satellites in low Earth orbit and extremely accurate clocks to provide information necessary to determine the location of the receiving device. The United States maintains one such constellation of satellites that is available to the military and other users.
A typical GPS device incorporates a receiver circuit for receiving signals from satellites and a processor that interprets the received signal in order to determine the GPS""s location relative to the satellites. Based upon the delay between the time signals that are sent by the satellites and the time that the signals are received, the distance between each of the satellites and the GPS receiver can be determined. Calculations based upon the distance between the receiver and the satellites can then be used to determine the receiver""s position and report it in terms of latitude, longitude, and altitude.
FIG. 1 illustrates an example of a typical GPS system 50. A GPS receive and decode circuit 20 includes a four-channel receiver 24 coupled to an antenna 22 that receives signals from satellites 10A, 10B, 10C and 10D. Responsive to the signals from satellites 10A and 10B, receiver 24 outputs a signal to decoder processor 26 that decodes the signals received from the satellites in order to generate a location signal 28. The location signal 28 is output from GPS receive and decode circuit 20. The location signal 28 may be further processed by interface processor 30 in order to generate a display signal 32 that drives a display 40 in order to output the location information from the satellites in a format useful to a user of the GPS.
GPS devices determine location by measuring the distance of the GPS device from four satellites of the constellation of satellites place in orbit. The satellites orbit at an altitude of 11,000 miles and all transmit a precise timing signal at the same carrier frequency. However, each satellite also transmits a unique pseudo-random code pattern that uniquely identifies the transmitting satellite. The GPS device therefore requires a four-channel receiver circuit to receive the signal from each satellite.
Decoder processor 26 maintains data on the location and pseudo-random code pattern for each transmitting satellite. The decoder determines its location by triangulating the distance values from the known position of each satellite. This requires the decoder processor 26 to select widely spaced satellites and measure their distance from the receiver by measuring a delay in the signal sent by each satellite. Once the distance of the GPS receiver 50 to each of the satellites is determined, then the processor 26 calculates the intersection of the sphere around each satellite having a radius equal to the distance of the satellite from the receiver. Typically two location values are obtained, one of which can usually be eliminated by assuming that receiver 50 is on the surface of the earth.
In order to compensate for an imperfect clock reference in the GPS receiver 50, the measurement to the fourth satellite is made in order to determine a correction factor that can be applied to the measurements involving the other three satellites. In addition, the decoder processor 26 may also compensate for atmospheric effects that can change the speed of the timing signals, such as by using a fixed model of the effect of the atmosphere or by performing a differential comparison of the atmosphere""s effect on signals having different frequencies. Furthermore, the timing signal from each satellite also includes corrected position information for the satellite to compensate for changes in the satellite""s orbit that processor 26 will process. GPS receiver 50 will also need to perform signal rejection in order to counteract ground effects caused by reflection of the timing signals from objects such as buildings and mountains.
The end result is that GPS receiver 50 outputs a digital value from processor 26 that represents the location of the receiver. Conventional satellite positioning systems are typically configured to report a user""s location via a numeric display. While this information is useful for navigation, it is limited in its overall utility since it simply displays the navigational coordinates of the user""s location, or similar information, and does not relate the location to important characteristics of the user""s location.
Other applications of GPS technology have resulted in equipment that can store a predetermined point, such as a user""s earlier position, a destination point, or another predetermined point, and, in combination with the current location, provide the cardinal direction the user must travel to move from the current location to the predetermined point. While this approach works well to enable a user to find the predetermined point, the system is unable to provide much additional information about the user""s location except for its position.
There exist useful sources of additional information regarding particular locations and their surroundings. For instance, maps have been available for centuries and are useful aids in orientation and trip planning. However, maps require a user to determine where they are located on the map and interpret the information contained in the map. Guide books also provide useful and detailed information about locations but also require the user to know where he is in order to extract the correct information from the books. Cassette tapes can provide tour-guide information, but the user is constrained to following the route determined by the sequence of locations referenced on the cassette tape.
Still other conventional devices combine location information with a map and the ability to provide directions to user-specified destinations. This technology is limited because it does not have the capability to provide additional informational content about passing locations, has no ability to allow the user to select content, and has no ability to update the content provided based upon the user""s references.
Therefore, the need remains for an approach that permits a user""s position to be coordinated with additional useful information relating to that position.
In accordance with preferred embodiments of the present invention, some of the problems associated with the use of geographically oriented information are overcome.
One aspect of the present invention includes a location sensitive method for outputting data from a database. The method includes the steps of receiving a current position value and searching a database for a database entry corresponding to the current position value. If a corresponding database entry is found, the method calls for outputting a contents of the corresponding database entry.
An embodiment of a location sensitive database apparatus, according to the present invention, includes a positioning system, configured to receive geographical reference signals and, responsive thereto, generate a location signal indicating a geographical position of the positioning system, and a content database configured to store database entries, each database entry corresponding to a geographic region and including machine readable data. The apparatus also has an output display configured to receive the machine readable data and output the machine readable data in a human recognizable format. A database processor of the apparatus is configured to receive the location signal from the positioning system and, responsive thereto, search the content database for a corresponding database entry where the geographic region of the corresponding database entry matches a current value of the location signal. If the database processor finds the corresponding database entry, it transfers the machine readable data for the corresponding database entry to the output display.
The foregoing and other features and advantages of a preferred embodiment of the present invention will be more readily apparent from the following detailed description, which proceeds with references to the accompanying drawings.